DBLookupComboBox  text property
lazarus / 16-Databases

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jack · 2012-09-08 22:47

I would like to Use a DBLookupComboBox to maintain a field in one
Query "datasource" and get the list of possible values from another
Query "listSource".  As it turns out the two queries are against the
same column in the same table. And yields a list of all the previously
entered values as options/

It works quite well until I need to add a new option.

I can type a new option into the edit box on the control but it is
discarded and replaced with an empty string.  I see the
DBLookupComboBox.Text property but it returns an empty string whenever
the edit does not match one of the options in the listsource.

Is there a way to get at the typed entry?

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taazz · 2012-09-08 23:42

Quote from: jack on September 09, 2012, 12:47:24 amI would like to Use
a DBLookupComboBox to maintain a field in one Query "datasource" and
get the list of possible values from another Query "listSource".  As
it turns out the two queries are against the same column in the same
table. And yields a list of all the previously entered values as
options/

that is a weird design.

Quote from: jack on September 09, 2012, 12:47:24 amIt works quite well
until I need to add a new option.

I can type a new option into the edit box on the control but it is
discarded and replaced with an empty string.  I see the
DBLookupComboBox.Text property but it returns an empty string whenever
the edit does not match one of the options in the listsource.

Is there a way to get at the typed entry?

No there is no way to accomplish that with a dblookupcombobox. A
dblookupcombobox has been designed to enforce a master/detail
relationship farther more it is designed to select a value looking at
different fields than the key field eg

data source = invoice
data field = custID
list source = customers table
list field = customer full name
key field = customerID

by selecting a customer name the lookup combo box will place the
customerID in the invoice.CustID field you can't use its editor to
select a value that does not exists because it can't much it to the
customerID field wasn't designed for free form editing.
You can use a dbcombobox but you have to manually populate with the
values you want to choose from and you have to use the values that are
going to inserted in the field you can't populate it with customer
name link it to custid you will a number of errors.

here is a procedure that given a dbcombobox a listdataset (not
datasource) and the field's name it will populate the the combobox for
you.

Code: [Select]procedure PopulateComboBox(aCombo:TDBComboBox;
ListDataset:TDataset; ListFieldName:string);
var
  bkmark : TBookmark;
  fld    : TField;
begin
  ListDataset.DisableControls;
  try
    fld := ListDataset.FieldByName(ListFieldName);
    bkmark:= ListDataset.GetBookmark;
    ListDataset.First;
    repeat
      aCombo.Items.Add(fld.AsString);
      ListDataset.Next;
    until ListDataset.EOF;
  finally
    ListDataset.GotoBookmark(bkmark);
    ListDataset.FreeBookmark(bkmark);
    ListDataset.EnableControls;
  end;
end;          

regards

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jack · 2012-09-09 18:25

Thank you all for your input.